Insulating electrophoretic paint, workpiece having insulating layer, battery pack, and electric device

Abstract

The application provides an insulating electrophoretic paint, a workpiece with an insulating layer, a battery pack and an electrical device. The insulating electrophoretic paint comprises a modified polyimide polymer, a silsesquioxane, a blocked isocyanate, an acid and water; wherein the silsesquioxane is modified with at least one amino group; at least one end of the modified polyimide polymer is a polyimide-like molecular chain, and the end of the polyimide-like molecular chain has a hydroxyalkyl-substituted amide group. The insulating layer prepared from the insulating electrophoretic paint has not only good electrical insulation performance, but also good high-temperature resistance and excellent low dielectricity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating, in particular to an insulating electrophoretic coating, a workpiece with an insulating layer, a battery pack and an electrical equipment. BACKGROUND

[0002] At present, new energy devices such as electric vehicles are generally powered by battery packs, which generally include a box body. The box body is usually divided into multiple accommodation cavities to accommodate battery cells. In order to ensure the safety performance of the battery pack, an insulating layer is generally provided on the inner wall of the accommodation cavity. At present, the commonly used coating method for the insulating layer of the accommodation cavity is spraying. However, it is difficult for the spraying process to form a uniform insulating layer on the inner wall of the accommodation cavity with a complex structure. Moreover, the commonly used insulating coating has poor high-temperature resistance, which cannot fully meet the insulating requirements of the battery pack. SUMMARY

[0003] In view of this, the present application provides an insulating electrophoretic coating. The insulating layer prepared from the insulating electrophoretic coating has not only good electrical insulation performance, but also good high-temperature resistance and excellent low dielectricity.

[0004] The first aspect of the present application provides an insulating electrophoretic coating, which comprises a modified polyimide polymer, a silsesquioxane, a blocked isocyanate, an acid and water. The silsesquioxane is modified with at least one amino group. At least one end of the modified polyimide polymer is a polyimide-like molecular chain, and the terminal of the polyimide-like molecular chain has a hydroxyalkyl-substituted amide group.

[0005] In the insulating electrophoretic coating provided by the present application, the above-mentioned blocked isocyanate molecule can form a chemical bond with the group on the silsesquioxane, and can also react with the hydroxyl group in the modified polyimide polymer at the same time to generate a cross-linked network structure, thereby obtaining a dense electrical insulation coating. The above-mentioned insulating layer can have good high-temperature resistance, excellent low dielectricity and good electrolyte resistance.

[0006] The second aspect of the present application provides a workpiece with an insulating layer, which is prepared by electrodeposition and curing of the insulating electrophoretic coating provided by the first aspect of the present application. Due to the presence of the above-mentioned insulating layer, the workpiece also has good electrical insulation performance, high-temperature resistance and low dielectricity, and has a wide application prospect.

[0007] The third aspect of the present application provides a battery pack, which comprises a box body and at least one battery cell accommodated in the box body. The box body is prepared from the workpiece provided by the second aspect of the present application. The battery pack has a good application prospect and can be used to provide an electrical equipment with good safety performance at high temperature.

[0008] The fourth aspect of the present application provides an electrical equipment, which comprises the battery pack provided by the third aspect of the present application. DETAILED DESCRIPTION

[0009] The embodiment of the present application provides an insulating electrophoretic paint, which comprises a modified polyimide polymer, a silsesquioxane, a blocked isocyanate, an acid and water; wherein the silsesquioxane is modified with at least one amino group; wherein at least one end of the modified polyimide polymer is a polyimide-like molecular chain, and the end of the polyimide-like molecular chain has a hydroxyalkyl-substituted amide group.

[0010] In the above insulating electrophoretic paint, the amino-modified silsesquioxane (POSS) has good hydrophilicity and thus has certain water solubility, and the POSS with the amino group and the modified polyimide polymer with the hydroxyl group can be positively charged under the action of the acid, so as to have high electrophoretic force; thus, under the action of an electric field, the modified polyimide polymer, the amino-modified silsesquioxane and the blocked isocyanate can all migrate to the cathode and deposit, and the hydroxyl group of the modified polyimide polymer and the amino group of the POSS can form chemical bonds with active groups in the blocked isocyanate molecules, so that the blocked isocyanate molecules form a composite crosslinking network structure as a "bridging group", and a uniform and dense coating is obtained, which can avoid the occurrence of undesirable phenomena such as POSS agglomeration; at the same time, the polyimide-like molecular chain in the modified polyimide polymer has excellent heat resistance, cold resistance, solvent resistance, radiation resistance, mechanical properties and insulating properties, the silsesquioxane has high heat resistance and excellent dielectric properties, and finally the formed coating can have good electrical insulation, high temperature performance and excellent low dielectric properties, and the modified polyimide polymer also has excellent electrolyte resistance, so the coating formed by the above paint can not only be used to improve the high temperature performance of the battery pack, but also can effectively reduce the dielectric loss of the battery pack. Therefore, the coating formed by the above paint can simultaneously have good electrical insulation, high temperature performance, excellent low dielectric properties and electrolyte resistance.

[0011] In addition, based on the electrophoretic characteristics of the above paint, the above paint is particularly suitable for insulating coating of irregular workpieces.

[0012] In some embodiments of the present application, the amino group is directly connected to the Si atom in the POSS body structure, or each amino group in the POSS is connected to the Si atom in the POSS body structure through at least one of an alkylene chain, an unsaturated alkylene chain, an epoxy group, an aromatic ring, etc. In some embodiments of the present application, the number of C atoms in the alkylene chain is 1-6, the number of C atoms in the unsaturated alkylene chain is 2-6, and the number of C atoms in the epoxy group is 2-6. Controlling the number of carbon atoms in the above groups makes each amino group in the POSS have a relatively appropriate steric hindrance, which is conducive to improving the reaction degree between the amino group and the isocyanate and improving the crosslinking degree of the aforementioned composite crosslinking network structure, and is also conducive to ensuring that the dielectric constant of the insulating layer is small. In some embodiments of the present application, the amino group is connected to the Si atom in the POSS body structure through a benzene ring, that is, one modified group of the POSS can be represented as (-C6H4NH2). In this way, the modified POSS can have water solubility and electrophoretic properties, and the steric hindrance of the POSS can be further improved, which can further reduce the dielectric constant of the insulating layer while ensuring the compactness of the insulating layer. In some specific embodiments, the amino group (-NH2) is in the para position or the meta position of the benzene ring with respect to the silicon atom. When the amino group and the silicon atom are in the para position or the meta position on the benzene ring, the steric hindrance between the amino group and the silicon atom is relatively small for a single POSS, so that each amino group on the POSS is more easily reacted with the blocked isocyanate, thereby further improving the crosslinking degree of the aforementioned composite crosslinking network structure, and further improving the compactness of the insulating layer, which is more conducive to improving the comprehensive performance of the final insulating layer.

[0013] In some embodiments of the present application, the POSS is simultaneously modified with an aniline group and a phenyl group, and the general structure of the POSS is (SiO 1.5 ) n (C6H5) x (C6H4NH2) y ; wherein n = 8, 10, or 12; x is any positive integer within 1-n; y = n-x, and y is a positive integer. The value of n can be 8, in which case the body structure of the POSS is octasilsesquioxane (T8); correspondingly, the value of x can be 1, 2, 3, 4, 5, 6, 7; and the value of y can be 7, 6, 5, 4, 3, 2, 1. The value of n can be 10, in which case the body structure of the POSS is decasilsesquioxane (T10); correspondingly, the value of x can be 1, 2, 3, 4, 5, 6, 7, 8, 9; and the value of y can be 9, 8, 7, 6, 5, 4, 3, 2, 1. The value of n can be 12, in which case the body structure of the POSS is dodecasilsesquioxane (T10); correspondingly, the value of x can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11; and the value of y can be 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.

[0014] It should be noted that in the present application, the insulating electrophoretic paint can contain multiple different POSS monomers at the same time. Specifically, in the insulating electrophoretic paint, the POSS monomers can be different in functional groups, different in the ratio between functional groups (i.e., different values of x, y), different in the value of n, and more different in two or three of the above factors.

[0015] In some embodiments of the present application, the value of y is in the range of 2-5. In this way, the solubility of POSS in water is further improved, so that a more uniform and stable emulsion is obtained, and the POSS can exhibit suitable electrical properties in the electrophoretic paint, which is more conducive to its deposition on the surface of the workpiece, and more importantly, the POSS can have a more suitable crosslinking degree with the blocked isocyanate, so that the final insulating layer has high compactness, excellent electrical insulation performance, and better high-temperature resistance.

[0016] For example, when the value of n is 8 and x = y = 4, the structure of (SiO 1.5 )8(C6H5)4(C6H4NH2)4 is shown in the following formula (1):

[0017] wherein R is a benzene ring, R' is

[0018] In some embodiments of the present application, the molar ratio of the hydroxyl groups in the modified polyimide-based polymer to the blocked isocyanate is 1:(0.1-0.6), and the molar ratio of the hydroxyl groups in the modified polyimide-based polymer to the blocked isocyanate can be, but is not limited to, 1:0.1, 1:0.3, 1:0.4, 1:0.5, or 1:0.6. In some embodiments, the molar ratio of the hydroxyl alkyl-substituted amide groups in the modified polyimide-based polymer to the acid is 1:(0.2-0.4). In this way, it is more conducive to controlling the formation of a dense network structure by the polymer, thereby improving the uniformity and insulation of the coating.

[0019] In some embodiments of the present application, the insulating electrophoretic paint comprises the following components by weight: 10-40 parts of modified polyimide polymer, 1-10 parts of amino-modified POSS, 5-30 parts of blocked isocyanate, 50-80 parts of water, and 0-20 parts of co-solvent. Controlling the above components within the above weight ranges can provide the paint with good uniformity and flowability, and when applied to electrophoretic coating, a uniform, dense, and excellent insulating coating with excellent electrical insulation, high-temperature resistance, and good dielectric properties can be obtained. For example, the modified polyimide polymer can be in a weight of 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 39, etc. For example, the amino-modified POSS can be in a weight of 1, 2, 3, 4, 5, 6, 7, 8, 9, etc. For example, the blocked isocyanate can be in a weight of 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, etc. For example, the water can be in a weight of 80, 55, 60, 65, 70, 75, 78, etc. In some embodiments of the present application, the above insulating electrophoretic paint can further comprise a co-solvent. The co-solvent can promote the dissolution of the modified polyimide polymer, silsesquioxane, and blocked isocyanate in water, form a uniform and stable emulsion, and be more conducive to the application of the insulating electrophoretic paint. For example, the co-solvent can be in a weight of 0.5, 1, 2, 5, 8, 10, 15, 18, etc. In the present application, the above co-solvent includes but is not limited to alcohol ether compounds. In some specific embodiments, the above co-solvent is selected from one or more of propylene glycol phenyl ether, propylene glycol phenyl ether, and propylene glycol butyl ether.

[0020] In some embodiments of the present application, the modified polyimide polymer is in a weight of 10-30 parts, the amino-modified POSS is in a weight of 2-8 parts, the blocked isocyanate is in a weight of 10-25 parts, the water is in a mass fraction of 60-80 parts, and the co-solvent is in a weight of 5-20 parts. In this way, the cross-linking degree of the cross-linked network structure formed by the above insulating electrophoretic paint after curing is more appropriate, the density of the insulating layer is higher, the high-temperature resistance, dielectric properties, and insulating properties of the insulating layer are more balanced, and the comprehensive performance is stronger.

[0021] In the present application, an acid is added to the insulating electrophoretic paint to adjust the pH thereof, and the acid in the insulating electrophoretic paint can be any one of inorganic acid or organic acid. In some embodiments, the acid comprises an organic acid, and the organic acid comprises one or more of formic acid, acetic acid, lactic acid, sulfamic acid, and guanidino acetic acid. For example, when the above acid is acetic acid, at least part of R’ in the above formula (1) is converted to R”, i.e., at least part of is converted to In some embodiments of the present application, the pH value of the above-mentioned insulating electrophoretic coating is 4-6. In this way, the modified polyimide polymer and the amino-modified POSS can have suitable electrical properties, and can be uniformly deposited on the surface of the workpiece under the action of an electric field. The coating can also have good stability. For example, the pH value of the insulating electrophoretic coating can be 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, etc.

[0022] In some embodiments of the present application, at least one end of the modified polyimide polymer is a polyimide-like molecular chain, and the end of the polyimide-like molecular chain has a hydroxyalkyl-substituted amide group. In some examples, the structure of the polyimide-like molecular chain on one side of the modified polyimide polymer is shown in formula (2-1) or formula (2-2):

[0023]

[0024] In formula (2-1), at least one of R1 and R2 is a hydroxy-substituted alkyl group, and the number of carbon atoms in the hydroxy-substituted alkyl group is 1-10; R3 can be a carboxyl group or an amide group. In formula (1-2), R1 is a hydroxy-substituted alkyl group, and the number of carbon atoms in the hydroxy-substituted alkyl group is 1-10; R3 can be a carboxyl group or an amide group. In formula (2-1) and formula (2-2), represents an imide repeating unit, the polyimide-like molecular chain is obtained by reaction of a diamine and a dianhydride, is a structure after dianhydride reaction, is a structure after diamine reaction.

[0025] In some embodiments of the present application, the number of hydroxyl groups in the hydroxyalkyl-substituted amide group is greater than or equal to 2, i.e., the number of hydroxyl groups in R1 and R2 is greater than or equal to 2. When the content of hydroxyl groups in the modified polyimide polymer is high, it is beneficial to increase the water solubility of the modified polyimide polymer, thereby obtaining a uniform and stable electrophoretic emulsion, and the modified polyimide polymer can also fully react with the blocked isocyanate to form a coating with good insulation performance. In some embodiments of the present application, a carboxylic acid can be used to adjust the pH value of the above-mentioned insulating electrophoretic coating, so that the end of the polyimide-like molecular chain also has a carboxyl group. The carboxyl group can also enhance the water solubility of the modified polyimide polymer, so that the modified polyimide polymer is uniformly dispersed in the coating, and then a uniform and relatively dense electrophoretic coating is formed.

[0026] In the embodiments of the present application, the modified polyimide polymer is composed of a polyimide-like molecular chain, and the modified polyimide polymer is a copolymer of polyimide. In some examples, the structure of the modified polyimide polymer is shown in formula (1-3) or formula (1-4):

[0027]

[0028]

[0029] In some embodiments of the present application, the molecular weight of the modified polyimide-like polymer composed of polyimide-like molecular chains is 3000 g / mol to 100000 g / mol. The molecular weight of the modified polyimide-like polymer composed of polyimide-like molecular chains can be, but is not limited to, 3000 g / mol, 5000 g / mol, 8000 g / mol, 10000 g / mol, 30000 g / mol, 50000 g / mol, 80000 g / mol or 100000 g / mol. In some embodiments, the molecular weight of the modified polyimide-like polymer composed of polyimide-like molecular chains is 5000 g / mol to 50000 g / mol. Controlling the molecular weight of the modified polyimide-like polymer can make the polymer have moderate hydrophilicity, which can stabilize the dispersion in the coating on the one hand, and on the other hand, the polymer particles can also be separated from water during electrodeposition, so that the coating layer with smooth surface and moderate thickness is uniformly deposited on the surface of the workpiece, ensuring that the coating layer has good insulation.

[0030] In some embodiments of the present application, the modified polyimide-like polymer further comprises an epoxy resin molecular chain, i.e., the modified polyimide-like polymer is a block copolymer of epoxy resin and polyimide. Epoxy resin has the advantages of high bonding strength, wide bonding surface and good processing performance, and can complement the performance of polyimide, which is conducive to obtaining a coating with strong adhesion. Moreover, the cost of epoxy resin is relatively low, and the combination of epoxy resin and polyimide can also reduce the product cost. In some embodiments, the structure of the modified polyimide-like polymer containing an epoxy resin molecular chain is shown in formula (3-1) or formula (3-2):

[0031]

[0032]

[0033] In the present application, the epoxy group in the epoxy resin reacts with the carboxyl group in the polyimide to form a block polymer, and in formula (3-1) and formula (3-2), represents the structure after the reaction of the epoxy resin, and in the modified polyimide-like polymer, the epoxy resin molecular chain is connected to the epoxy resin molecular chain through a carbon-oxygen bond.

[0034] In some embodiments of the present application, the molecular chain of the epoxy resin comprises one or more of glycidyl structure and non-glycidyl structure. In some embodiments, the molecular chain of the epoxy resin comprises glycidyl structure, and further, the molecular chain of the epoxy resin comprises glycidyl ether structure. The ether bond in the molecular chain segment of the glycidyl ether structure can rotate intramolecularly, so that the flexibility of the polymer chain is strong, which is conducive to improving the flexibility of the coating.

[0035] In some embodiments of the present application, the mass percentage content of the molecular chain of the epoxy resin in the modified polyimide-like polymer is 25% to 50%. In some embodiments of the present application, the mass ratio of the polyimide-like molecular chain to the molecular chain of the epoxy resin in the modified polyimide-like polymer is (1-3):1. The mass ratio of the polyimide-like molecular chain to the molecular chain of the epoxy resin can be, but is not limited to, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1. Controlling the mass ratio of the polyimide-like molecular chain to the molecular chain of the epoxy resin is conducive to obtaining a modified polyimide-like polymer with good high-temperature resistance and high bonding strength, so as to ensure that the coating can strongly protect the workpiece.

[0036] In some embodiments of the present application, the molar ratio of the hydroxyalkyl-substituted amide group to the acid in the modified polyimide-like polymer is 1:(0.1-0.8), and the molar ratio of the hydroxyalkyl-substituted amide group to the acid in the modified polyimide-like polymer can be, but is not limited to, 1:0.1, 1:0.3, 1:0.5, 1:0.6 or 1:0.8. In some embodiments, the molar ratio of the hydroxyalkyl-substituted amide group to the acid in the modified polyimide-like polymer is 1:(0.4-0.6).

[0037] In the present application, the blocked isocyanate is prepared from a blocking agent and an isocyanate, and the blocked isocyanate can react with the modified polyimide-based polymer to form a dense cross-linked network structure, which is conducive to improving the insulation performance of the coating. In some embodiments of the present application, the blocking agent includes one or more of a lactam compound, an oxime compound, a phenol compound, an aliphatic alcohol compound or an ether alcohol compound; and the isocyanate includes one or more of an aromatic polyisocyanate compound and a modified body thereof, and an alicyclic polyisocyanate compound and a modified body thereof. In some embodiments, the polyisocyanate includes an aromatic polyisocyanate compound and a modified body thereof, and the aromatic polyisocyanate compound contains an aromatic ring, which has high stability and is conducive to improving the high-temperature resistance of the coating. In some embodiments, the blocking agent includes one or more of diethylene glycol ethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, isooctanol, methyl ethyl ketone oxime, methyl amyl ketone oxime, acetone oxime, 3,5-dimethylpyrazole, p-tert-butyl phenol, cresol, ε-caprolactam, and γ-butyrolactam; and the polyisocyanate includes one or more of toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, xylylene diisocyanate, naphthalene-1,5-diisocyanate, and tetramethylxylylene diisocyanate. In the present application, the blocked isocyanate can also be a commercially available product.

[0038] In some embodiments of the present application, the preparation method of the above-mentioned insulating electrophoretic paint can include the following steps:

[0039] S01, adding a cosolvent, an amino-modified POSS, a blocked isocyanate, and water to a container containing a modified polyimide-based polymer, stirring for 15-30 min to obtain a mixture;

[0040] S02, slowly adding an acid to the above-mentioned mixture, and reacting at 20-40°C for 0.5-1 h, and controlling the pH value of the system to be between 5.5 and 6.8.

[0041] In some embodiments of the present application, in step S01, the stirring time is 20-30 min.

[0042] In some embodiments of the present application, in S02, the acid is slowly added to the above-mentioned mixture, and reacted at 25-35°C for 30-40 min, and the pH value of the system is controlled to be between 5.5 and 6.8. In some embodiments of the present application, in step S02, after adjusting the pH of the system to 5.5-6.8, deionized water can be further added to the above-mentioned mixture to dilute to the target concentration. It can also be that the insulating electrophoretic paint provided by the present application is directly obtained when the pH of the system is adjusted to 5.5-6.8, so as to facilitate storage and transportation. Before the above-mentioned insulating electrophoretic paint is used for electrophoresis treatment by a person skilled in the art, deionized water is added to dilute the insulating electrophoretic paint to the target concentration, so as to facilitate use.

[0043] In some embodiments of the present application, the solid content of the insulating electrophoretic paint is 15% to 25%. In the present application, the solid content of the insulating electrophoretic paint refers to the ratio of the total mass of the modified polyimide polymer and the mass of the POSS to the total mass of the insulating electrophoretic paint.

[0044] The present application also provides a workpiece with an insulating layer prepared by electrodeposition and curing of the insulating electrophoretic paint provided by the embodiments of the present application. Thus, the workpiece not only has excellent electrical insulation performance, but also can maintain high insulation performance after being in a high-temperature environment for a long time, and the workpiece has low dielectric loss and good electrolyte resistance, and is particularly suitable for preparing a battery pack containing cavity.

[0045] In some embodiments of the present application, the above workpiece can be prepared according to the following steps:

[0046] (1) Soaking the workpiece in the aforementioned insulating electrophoretic paint, connecting to the cathode of the electrophoresis device, inserting the auxiliary anode, and conducting electricity to perform electrophoresis treatment to obtain a pre-prepared workpiece. The voltage of the electrophoresis is 80V-180V, and the electrophoresis time is 3min-6min;

[0047] (2) Washing the above pre-prepared workpiece for 3-4 times, and baking at 170℃-190℃ for 20min-40min to obtain a workpiece with an insulating layer.

[0048] In some specific embodiments of the present application, in step (1), the voltage of the electrophoresis is 100V-150V; and the electrophoresis time is 3min-5min.

[0049] In some specific embodiments of the present application, in step (2), the baking temperature is 175℃-185℃; and the baking time is 25min-35min.

[0050] In some embodiments of the present application, in order to further optimize the effect, the workpiece can be first made into a battery pack box, the box includes a containing cavity, the aforementioned insulating electrophoretic paint is poured into the containing cavity, the box is connected to the cathode of the electrophoresis device, and the auxiliary anode is directly inserted into the containing cavity, electricity is conducted, electrophoresis treatment is performed to obtain a pre-prepared workpiece, and then baking is performed to obtain a battery pack box with an insulating layer on the inner wall of the containing cavity.

[0051] The embodiments of the present application also provide a battery pack including a box and at least one electric core accommodated in the box, and the box is prepared from the workpiece provided by the embodiments of the present application or includes the aforementioned battery pack box with an insulating layer in the containing cavity. The safety performance of the above battery pack is good, especially the insulation safety performance under high temperature, and the dielectric loss of the battery pack is low.

[0052] The application provides a kind of power utilization equipment, including the battery pack provided in the application.The power utilization equipment has more wide market prospect and high market competitiveness due to the adoption of the battery pack provided in the application.

[0053] The technical scheme of the application is further illustrated in the following embodiments.

[0054] Embodiment 1

[0055] Under nitrogen atmosphere, 17.45 g (80 mmol) of pyromellitic dianhydride and 12.01 g (60 mmol) of 4,4'-oxydianiline were added to 100 g of N-methylpyrrolidone solvent, and reacted at 25°C for 6 hours to obtain an anhydride-terminated polyamic acid (a-PAA) solution with a certain molecular weight. The number average molecular weight Mn of the polyamic acid was 3700 g / mol, and the polymer polydispersity index PDI was 1.09, as determined by gel permeation chromatography. 20 g of xylene was added to the anhydride-terminated polyamic acid (a-PAA) solution, and refluxed at 180°C for 4 hours until no water was added to the water separator. An anhydride-terminated polyimide (a-PI) solution was obtained. 1.67 g (15.92 mmol) of diethanolamine was added to the anhydride-terminated polyimide (a-PI) solution, and reacted at 25°C for 4 hours to obtain an amine-modified polyimide (d-PI) solution. 4.96 g (26.53 mmol) of E51 epoxy resin (epoxy equivalent weight 184-190 g / eq) was added to the amine-modified polyimide (d-PI) solution, and reacted at 50°C for 4 hours to obtain a polyimide-modified epoxy resin (PI-b-EP) solution A1.

[0056] In a container, 25 parts by weight of the above-mentioned solution A1, 10 parts by weight of a cosolvent (specifically, propylene glycol phenyl ether), 4 parts of an amino-modified silsesquioxane (whose structure is shown in formula (A)), 10 parts by weight of a blocked isocyanate (BL5335 from Covestro), and 51 parts of deionized water were added, stirred for 25 min, and acetic acid was slowly added. The system was reacted at 30°C for 0.5 h, and the pH value was adjusted to 6.5 to obtain an insulating electrophoretic coating B1.

[0057] The structure of the aforementioned amino-modified silsesquioxane is shown in the following formula:

[0058] wherein R is a benzene ring, and R' is

[0059] Deionized water was added to B1 to dilute it to a solid content of 20±2%, and the diluted B1 was poured into the accommodating cavity of the pretreated battery pack box body. The box body was connected to the cathode of an electrophoresis device, an auxiliary anode was inserted into the accommodating cavity, and electrophoresis treatment was performed under an electrophoresis voltage of 120 V for 5 min to obtain a preform. After the preform was washed with water three times, it was baked at 180 °C for 30 min to obtain a battery pack box body C1 with an insulating layer on the inner wall of the accommodating cavity.

[0060] Example 2

[0061] The difference from Example 1 is that the insulating electrophoretic paint comprises the following components by weight: 25 parts by weight of the above-mentioned solution A1, 1 part by weight of a silsesquioxane as shown in formula (A), 10 parts of a blocked isocyanate (BL5335 from Covestro), 10 parts of a cosolvent, and 54 parts of deionized water, which are stirred uniformly, acetic acid is slowly added dropwise, and the system is reacted at 25 °C for 30 min. The pH value of the system is adjusted to 6 to obtain an insulating electrophoretic paint B2.

[0062] Deionized water was added to B2 to dilute it to a solid content of 20±2%, and the diluted B2 was poured into the accommodating cavity of the pretreated battery pack box body. The box body was connected to the cathode of an electrophoresis device, an auxiliary anode was inserted into the accommodating cavity, and electrophoresis treatment was performed under an electrophoresis voltage of 120 V for 5 min to obtain a preform. After the preform was washed with water three times, it was baked at 80 °C for 15 min and at 180 °C for 30 min to obtain a battery pack box body C2 with an insulating layer on the inner wall of the accommodating cavity.

[0063] Example 3

[0064] The difference from Example 2 is only that the insulating electrophoretic paint does not contain a cosolvent. An insulating electrophoretic paint B3 is obtained.

[0065] Deionized water was added to B3 to dilute it to a solid content of 20±2%, and the diluted B3 was poured into the accommodating cavity of the pretreated battery pack box body. The box body was connected to the cathode of an electrophoresis device, an auxiliary anode was inserted into the accommodating cavity, and electrophoresis treatment was performed under an electrophoresis voltage of 120 V for 5 min to obtain a preform. After the preform was washed with water three times, it was baked at 80 °C for 15 min and at 180 °C for 30 min to obtain a battery pack box body C3 with an insulating layer on the inner wall of the accommodating cavity.

[0066] Example 4

[0067] The difference from Example 1 is that the insulating electrophoretic paint comprises the following components by weight: 25 parts by weight of the above-mentioned solution Al, 10 parts by weight of the silsesquioxane as shown in formula (A), 10 parts by weight of blocked isocyanate (BL5335 from Covestro) and 45 parts of deionized water, 10 parts by weight of a cosolvent (specifically, propylene glycol phenyl ether) are stirred uniformly, acetic acid is slowly added dropwise, and the system is reacted at room temperature for 1 h, the pH value of the system is adjusted to 6.2, and an insulating electrophoretic paint B4 is obtained.

[0068] Deionized water is added to B4 to dilute it to a solid content of 20±2% of B4, and the above-mentioned diluted B4 is poured into the accommodating cavity of the pretreated battery pack box body, the box body is connected to the cathode of the electrophoretic device, an auxiliary anode is inserted into the accommodating cavity, and the electrophoretic treatment is carried out under the condition of an electrophoretic voltage of 120 V for 5 min to obtain a preform; after the preform is washed with water for 3 times, it is baked at 100°C for 10 min and at 180°C for 30 min to obtain a battery pack box body C4 with an insulating layer on the inner wall of the accommodating cavity.

[0069] Example 5

[0070] The difference from Example 1 is that the insulating electrophoretic paint comprises the following components by weight: 25 parts by weight of the above-mentioned solution Al, 10 parts by weight of the silsesquioxane as shown in formula (A), 10 parts by weight of blocked isocyanate (BL5335 from Covestro) and 45 parts of deionized water, 10 parts by weight of a cosolvent (specifically, propylene glycol phenyl ether) are stirred uniformly, acetic acid is slowly added dropwise, and the system is reacted at room temperature for 1 h, the pH value of the system is adjusted to 6.2, and an insulating electrophoretic paint B4 is obtained.

[0071] Deionized water is added to B5 to dilute it to a solid content of 20±2% of B5, and the above-mentioned diluted B5 is poured into the accommodating cavity of the pretreated battery pack box body, the box body is connected to the cathode of the electrophoretic device, an auxiliary anode is inserted into the accommodating cavity, and the electrophoretic treatment is carried out under the condition of an electrophoretic voltage of 120 V for 5 min to obtain a preform; after the preform is washed with water for 3 times, it is baked at 100°C for 10 min and at 180°C for 30 min to obtain a battery pack box body C4 with an insulating layer on the inner wall of the accommodating cavity.

[0072] Example 6

[0073] The difference from Example 1 is that the weight fractions of the components in the insulating electrophoretic paint are changed to obtain an insulating electrophoretic paint B6.

[0074] Deionized water was added to B6 to dilute to a solid content of 20±2% of B6, and the diluted B6 was poured into the accommodating cavity of the pre-processed battery pack box body. The box body was connected to the cathode of the electrophoresis device, and an auxiliary anode was inserted into the accommodating cavity. The electrophoresis treatment was carried out under the condition of an electrophoresis voltage of 120 V for 5 min to obtain a preform. After the preform was washed with water for 3 times, it was baked at 120°C for 10 min and at 190°C for 20 min to obtain a battery pack box body C6 with an insulating layer on the inner wall of the accommodating cavity.

[0075] Example 7

[0076] The difference from Example 1 is that the weight fractions of the components in the insulating electrophoretic paint are changed to obtain an insulating electrophoretic paint B7.

[0077] Deionized water was added to B7 to dilute to a solid content of 20±2% of B7, and the diluted B7 was poured into the accommodating cavity of the pre-processed battery pack box body. The box body was connected to the cathode of the electrophoresis device, and an auxiliary anode was inserted into the accommodating cavity. The electrophoresis treatment was carried out under the condition of an electrophoresis voltage of 120 V for 5 min to obtain a preform. After the preform was washed with water for 3 times, it was baked at 120°C for 10 min and at 190°C for 20 min to obtain a battery pack box body C7 with an insulating layer on the inner wall of the accommodating cavity.

[0078] Example 8

[0079] The difference from Example 1 is that the structure of the silsesquioxane in the insulating electrophoretic paint is shown as formula (B). The obtained insulating electrophoretic paint is denoted as B8.

[0080] The structure of the aforementioned amino-modified silsesquioxane is shown as the following formula:

[0081] Wherein, R3 is a benzene ring, and R4 is —CH2NH2.

[0082] Deionized water was added to B8 to dilute to a solid content of 20±2% of B8, and the diluted B8 was poured into the accommodating cavity of the pre-processed battery pack box body. The box body was connected to the cathode of the electrophoresis device, and an auxiliary anode was inserted into the accommodating cavity. The electrophoresis treatment was carried out under the condition of an electrophoresis voltage of 120 V for 5 min to obtain a preform. After the preform was washed with water for 3 times, it was baked at 80°C for 15 min and at 190°C for 20 min to obtain a battery pack box body C8 with an insulating layer on the inner wall of the accommodating cavity.

[0083] Example 9

[0084] The difference from Example 1 is that the structure of the silsesquioxane in the insulating electrophoretic paint is shown as formula (B). The obtained insulating electrophoretic paint is denoted as B9.

[0085] wherein the aforementioned amino-modified silsesquioxane has the following structure:

[0086] wherein R3 is a benzene ring, R' is

[0087] Deionized water is added to B9 to dilute it to a solid content of 20±2%, and the diluted B9 is poured into the accommodating cavity of the pretreated battery pack box body, the box body is connected to the cathode of the electrophoresis device, and an auxiliary anode is inserted into the accommodating cavity. The electrophoresis treatment is carried out under the condition that the electrophoresis voltage is 100 V for 5 min to obtain a preform. After the preform is washed with water for 3 times, it is baked at 80°C for 15 min and at 190°C for 20 min to obtain a battery pack box body C9 with an insulating layer on the inner wall of the accommodating cavity.

[0088] Example 10

[0089] Under a nitrogen atmosphere, 17.45 g (80 mmol) of pyromellitic dianhydride and 15.02 g (75 mmol) of 4,4'-oxydianiline are added to 100 g of N-methylpyrrolidone solvent, and the reaction is carried out at 25°C for 6 hours to obtain an anhydride-terminated polyamic acid (a-PAA) solution with a certain molecular weight. The number average molecular weight Mn of the polyamic acid is 12700 g / mol, and the polymer polydispersity index PDI = 1.12, which is tested by gel permeation chromatography. 20 g of xylene is added to the anhydride-terminated polyamic acid (a-PAA) solution, and the refluxing is carried out at 180°C until no water is added to the water separator. The reaction is carried out for 4 hours to obtain an anhydride-terminated polyimide (a-PI) solution. 0.54 g (5.11 mmol) of diethanolamine is added to the anhydride-terminated polyimide (a-PI) solution, and the reaction is carried out at 25°C for 4 hours to obtain an amine-modified polyimide (d-PI) solution. 1.59 g (8.52 mmol) of E51 epoxy resin (epoxy equivalent weight 184-190 g / eq) is added to the amine-modified polyimide (d-PI) solution, and the reaction is carried out at 50°C for 4 hours to obtain a polyimide-modified epoxy resin (PI-b-EP) solution A2.

[0090] In a container, 15 parts by weight of the above product A2, 15 parts by weight of a cosolvent (propylene glycol phenyl ether), 8 parts by weight of a silsesquioxane represented by formula (A), 15 parts by weight of a blocked isocyanate (BL5335 from Covestro), and 47 parts by weight of deionized water are added and stirred uniformly for 30 min. Slowly dropwise addition of glacial acetic acid is carried out for acid neutralization reaction, the reaction temperature is 25°C, the reaction time is 25 min, and the Ph value is adjusted and controlled to 6.0 to obtain an insulating electrophoretic paint B10.

[0091] The B10 is diluted with deionized water to a solid content of 20±2%, and the diluted B10 is poured into the accommodating cavity of the pre-processed battery pack case body. The case body is connected to the cathode of the electrophoresis device, and an auxiliary anode is inserted into the accommodating cavity. The preform is obtained by electrophoresis treatment under the condition of an electrophoresis voltage of 150V for 4min. The preform is washed with water for 3 times, and then baked at 190℃ for 20min to obtain the battery pack case body C10 with an insulating layer on the inner wall of the accommodating cavity.

[0092] For the convenience of reading, the parameters of the electrophoretic insulating coating of each embodiment are summarized in Table 1.

[0093] Table 1

[0094]

[0095]

[0096] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0097] Comparative Example 1

[0098] The difference from Example 3 is that the electrophoretic insulating coating does not contain silsesquioxane. The obtained battery pack case body is denoted as DC1.

[0099] Comparative Example 2

[0100] A commercially available dip-coating insulating paint is used to form an insulating layer on the inner wall of the accommodating cavity of the battery pack case body by dip-coating process. The obtained battery pack case body is denoted as DC2.

[0101] Performance Test

[0102] (1) Insulating layer film thickness test: The film thickness data of different areas of the inner wall of the accommodating cavity of the battery pack case body are tested by using a film thickness tester. Ten points of each sample are tested, and the results are summarized in Table 2.

[0103] (2) Insulating layer adhesion test: The coating adhesion test is carried out on the inner wall of the accommodating cavity of the battery pack case body according to GB / T9286 “Cross-hatch test for pigmented and clear coatings”. The results are summarized in Table 3.

[0104] (3) Ambient temperature electrical insulation performance test: The voltage resistance test is carried out according to GB / T1408.1-2006 “Insulating materials-Test methods for electrical strength-Part 1: Test at power frequency”. Specifically, the voltage resistance is 1.5KV under AC for 60s, and the leakage current is less than 10mA; the voltage resistance is 1.5KV under DC for 60s, and the leakage current is less than 10mA, which is considered to pass. The results are summarized in Table 3.

[0105] (4) High temperature resistance test: bake the battery pack box sample of each example and the comparative example at 500℃ for 10 min, and observe the appearance change of the insulation layer. The results are summarized in Table 3.

[0106] (5) Electrical insulation performance test after high temperature: according to GB / T 1408.1-2006 "Insulating materials - Determination of the electrical strength - Part 1: Test at power frequency", the voltage resistance test is performed again on each sample after the high temperature resistance test of step (4). Specifically, the voltage resistance is 1.5KV AC for 60s, and the leakage current is less than 10mA; the voltage resistance is 1.5KV DC for 60s, and the leakage current is less than 10mA, which is considered to pass. The results are summarized in Table 3.

[0107] (6) Dielectric constant test: after stripping the insulation layer of the battery pack box of each example and the comparative example, a film with a size of 100mm x 100mm x 40μm is prepared, and the dielectric constant thereof is tested. According to GB / T 1409, the recommended method for measuring the permittivity and dielectric loss factor of electrical insulation materials at power frequency, audio frequency, and high frequency (including microwave wavelength), the test frequency is 50Hz. The results are summarized in Table 3.

[0108] (7) Electrolyte resistance test: drop the electrolyte commonly used in liquid batteries on the insulation layer of each example and the comparative example sample, and observe the appearance change of the insulation layer after standing at room temperature for 3 days. The results are summarized in Table 3.

[0109] Table 2

[0110]

[0111] Table 3

[0112]

[0113]

[0114] According to the data in Table 1 and Table 2, it can be seen that, compared with the comparative example insulating electrophoretic coating, the insulating electrophoretic coating provided in the examples of the present application can form an insulation layer with high uniformity on the surface of the workpiece, the dielectric constant of the insulation layer is low, and the adhesion between the insulation layer and the workpiece, the insulation performance of the insulation layer are all good, and the insulation layer still has insulation effect after baking at 500℃ for 10 min, and the insulation layer has electrolyte resistance.

[0115] Comparing the data between Comparative Example 1 and Examples 2-7, it can be found that the insulating electrophoretic paint further contains a cosolvent, and when the content of each component substance is within the range further provided in the present application, the comprehensive effect of the insulating layer formed thereby is better; comparing the data between Comparative Example 1 and Example 8, it can be found that the presence of benzene ring can indeed further increase the internal resistance of POSS, and is more conducive to reducing the dielectric constant of the insulating layer; comparing the data between Comparative Example 1 and Example 9, it can be found that when the number of amino groups in a single POSS is within the range further provided in the present application, the comprehensive performance of the insulating layer is better.

[0116] The above describes the exemplary embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. An insulating electrophoretic coating, characterized in that: The invention comprises a modified polyimide polymer, silsesquioxane, a blocked isocyanate, an acid and water; wherein the silsesquioxane is modified with at least one amino group; at least one end of the modified polyimide polymer is a polyimide-like molecular chain, and the end of the polyimide-like molecular chain has an amide group substituted with a hydroxyalkyl group; The insulating electrophoretic coating comprises the following components in parts by weight: 10 to 40 parts of a modified polyimide polymer, 1 to 10 parts of the silsesquioxane, 5 to 30 parts of the blocked isocyanate, 50 to 80 parts of water, and 0 to 20 parts of a cosolvent; the general structural formula of the silsesquioxane is (SiO 1.5 ) n (C6H5) x (C6H4NH2) y ; wherein n=8, 10 or 12; x is any positive integer from 1 to n; y=nx, and y is a positive integer in the range of 2 to 5.

2. The insulating electrophoretic coating according to claim 1, characterized in that: The amino group is connected to the Si atom in the silsesquioxane via a benzene ring, and the amino group and the Si atom are in the para position or meta position on the benzene ring.

3. The insulating electrophoretic coating according to claim 1 or 2, characterized in that: The pH value of the insulating electrophoretic coating is 5.5-6.

8.

4. The insulating electrophoretic coating according to claim 1 or 2, characterized in that: The modified polyimide polymer further comprises an epoxy resin molecular chain, and the epoxy resin molecular chain is connected to the polyimide-like molecular chain via a carbon-hydrogen bond.

5. A workpiece having an insulating layer, characterized in that: The insulating layer is prepared by electrodeposition and curing of the insulating electrophoretic coating according to any one of claims 1 to 4.

6. A battery pack, characterized in that: The invention comprises a box body and at least one battery cell accommodated in the box body, wherein the box body is made of the workpiece according to claim 5.

7. An electrical device, characterized in that: The electric device includes the battery pack as claimed in claim 6.

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